HTLV-1 is a human lymphotrophic retrovirus which causes adult T-cell leukemia/lymphoma and tropic spastic paraparesis/HTLV-1-associated myelopathy. These HTLV-1 associated diseases are endemic in Japan and the Caribbean, with sporadic occurrences in the U.S. Detection of HTLV-1 is typically done by immunological or polymerase chain reaction assays (see, e.g., Meytes, et al., Lancet 336(8730):1533-1535, 1990).
Commonly owned U.S. Pat. No. 4,868,105, issued Sep. 19, 1989describes a solution phase nucleic acid sandwich hybridization assay in which analyte nucleic acid is first hybridized in solution to a labeling probe set and to a capturing probe set in a first vessel. The probe-analyte complex is then transferred to a second vessel that contains a solid-phase-immobilized probe that is substantially complementary to a segment of the capturing probes. The segments hybridize to the immobilized probe, thus removing the complex from solution. Having the analyte in the form of an immobilized complex facilitates subsequent separation steps in the assay. Ultimately, single stranded segments of the labeling probe set are hybridized to labeled probes, thus permitting the analyte-containing complex to be detected via a signal generated directly or indirectly from the label.
Commonly owned European Patent Application (EPA) 883096976 discloses a variation in the assay described in U.S. Pat. No. 4,868,105, issued Sep. 19, 1998, in which the signal generated by the labeled probes is amplified. The amplification involves the use of nucleic acid multimers. These multimers are branched polynucleotides that are constructed to have a segment that hybridizes specifically to the analyte nucleic acid or to a nucleic acid (branched or linear) that is bound to the analyte and iterations of a second segment that hybridize specifically to the labeled probe. In the assay employing the multimer, the initial steps of hybridizing the analyte to label or amplifier probe sets and capturing probe sets in a first vessel and transferring the complex to another vessel containing immobilized nucleic acid that will hybridize to a segment of the capturing probes are followed. The multimer is then hybridized to the immobilized complex and the labeled probes in turn hybridized to the second segment iterations on the multimer. Since the multimers provide a large number of sites for label probe attachment, the signal is amplified. Amplifier and capture probe sequences are disclosed for Hepatitis B virus, Neisseria gonorrhoeae, penicillin and tetracycline resistance in N. gonorrhoeae, and Chlamydia trachomatis.
Commonly owned copending application Ser. No. 558,897, filed Jul. 27, 1990, describes the preparation of large comb-type branched polynucleotide multimers for use in the above-described solution phase assay. The combs provide greater signal enhancement in the assays than the smaller multimers.